1. Field of the Invention
The invention relates to high resolution digital image capturing, in particular, to a high resolution digital image capturing apparatus and a reference pixel memory storage space configuration method applied in the high resolution digital image capturing apparatus.
2. Description of the Prior Art
With the development of the technology, various kinds of image capturing apparatuses with different functions, for example, a mobile camera, a webcam, and a computer camera, have been widely applied in our daily life. In recent years, because ordinary consumers have more and more demands for image resolution, image capturing apparatuses with high resolution digital image capturing function have been developed to meet the requirements of the consumers.
In general, these high resolution digital image capturing apparatuses use the digital video coder/decoder standard with high compression ratio, for example, H.264/MPEG-4 AVC, to perform video coding/decoding to provide the digital image with high resolution. However, for these digital video coder/decoder standards with high compression ratio, it is important to properly and efficiently configure the memory space of the high resolution digital image capturing apparatus. Especially, for some video compression methods determining the digital video compression efficiency by referencing other reference frames, for example, an inter-prediction method, how to properly and efficiently configure the memory space is a problem needed to be solved.
Taking the inter-prediction method for example, the inter-prediction method references several frames previous to a current frame to calculate the current frame, and the high resolution digital image capturing apparatus usually stores all possibly referenced frames in a reference pixel memory space. The reference pixel memory space storing the referenced frames will not be released until the calculation of the current frame is finished. Please refer to FIG. 1. FIG. 1 illustrates a schematic diagram of an embodiment of performing the inter-prediction method.
As shown in FIG. 1, when a current search macro block B2 in a second frame F2 is calculated, pixels in a search range window W1 in a first frame F1 previous to the second frame F2 will be used as referenced pixels. In the same way, when a current search macro block B3 in a third frame F3 is calculated, pixels in a search range window W2 in the second frame F2 previous to the third frame F3 will be used as referenced pixels. Therefore, the reference pixel memory space of the high resolution digital image capturing apparatus should be large enough to store at least two reference frames to meet the requirement of the inter-prediction method.
For example, as shown in FIG. 2, a reference pixel memory 1 of a conventional high resolution digital image capturing apparatus includes a first storage space 10 and a second storage space 12. When the high resolution digital image capturing apparatus is calculating a third frame F3, the first storage space 10 and the second storage space 12 are used to store a first frame F1 and a second frame F2 previous to the third frame F3 respectively. However, in practical applications, once the search range window moves from a first region of the first storage space 10 down to a second region, the reference pixels stored in the first region will not be referenced again, therefore, the first region of the first storage space 10 will become a no longer referenced space, and the storage space of the reference pixel memory 1 will be wasted.
Therefore, the invention provides a high resolution digital image capturing apparatus and a reference pixel memory storage space configuration method to solve the above-mentioned problems occurred in the prior arts.